FtpWebRequest.UsePassive 属性

定义

命名空间:

System.Net

程序集:

System.Net.Requests.dll

Source:

FtpWebRequest.cs

获取或设置客户端应用程序的数据传输过程的行为。

public:
 property bool UsePassive { bool get(); void set(bool value); };

public bool UsePassive { get; set; }

member this.UsePassive : bool with get, set

Public Property UsePassive As Boolean

属性值

Boolean

如果客户端应用程序的数据传输过程侦听数据端口上的连接，则为 false；如果客户端应在数据端口上启动连接，则为 true。 默认值是 true。

例外

InvalidOperationException

对于一个已在进行的请求为此属性指定了一个新值。

示例

下面的代码示例检索并显示指定 FtpWebRequest 对象的属性值。

private:
   // DisplayRequestProperties prints a request's properties.
   // This method should be called after the request is sent to the server.
   static void DisplayRequestProperties( FtpWebRequest^ request )
   {
      Console::WriteLine( "User {0} {1}", request->Credentials->GetCredential( request->RequestUri, "basic" )->UserName, request->RequestUri );

      Console::WriteLine( "Request: {0} {1}", request->Method, request->RequestUri );

      Console::WriteLine( "Passive: {0}  Keep alive: {1}  Binary: {2} Timeout: {3}.", request->UsePassive, request->KeepAlive, request->UseBinary, request->Timeout == -1 ? "none" : request->Timeout.ToString() );

      IWebProxy^ proxy = request->Proxy;
      if ( proxy )
      {
         Console::WriteLine( "Proxy: {0}", proxy->GetProxy( request->RequestUri ) );
      }
      else
      {
         Console::WriteLine( "Proxy: (none)" );
      }

      Console::WriteLine( "ConnectionGroup: {0}", request->ConnectionGroupName == nullptr ? "none" : request->ConnectionGroupName );

      Console::WriteLine( "Encrypted connection: {0}", request->EnableSsl );

      Console::WriteLine("Method: {0}", request->Method);
   }

// DisplayRequestProperties prints a request's properties.
// This method should be called after the request is sent to the server.

private static void DisplayRequestProperties(FtpWebRequest request)
{
    Console.WriteLine("User {0} {1}",
        request.Credentials.GetCredential(request.RequestUri,"basic").UserName,
        request.RequestUri
    );
    Console.WriteLine("Request: {0} {1}",
        request.Method,
        request.RequestUri
    );
    Console.WriteLine("Passive: {0}  Keep alive: {1}  Binary: {2} Timeout: {3}.",
        request.UsePassive,
        request.KeepAlive,
        request.UseBinary,
        request.Timeout == -1 ? "none" : request.Timeout.ToString()
    );
    IWebProxy proxy = request.Proxy;
    if (proxy != null)
    {
        Console.WriteLine("Proxy: {0}", proxy.GetProxy(request.RequestUri));
    }
    else
    {
        Console.WriteLine("Proxy: (none)");
    }

    Console.WriteLine("ConnectionGroup: {0}",
        request.ConnectionGroupName == null ? "none" : request.ConnectionGroupName
    );

    Console.WriteLine("Encrypted connection: {0}",
        request.EnableSsl);

    Console.WriteLine("Method: {0}", request.Method);
}

注解

将 UsePassive 属性设置为 会将 true “PASV" 命令发送到服务器。 此命令请求服务器侦听数据端口并等待连接，而不是在收到传输命令时启动连接。

有关使用 UsePassive指定的行为的说明，请参阅 RFC 959：“文件传输协议”、第 3.2 节：“建立数据Connections”和第 4.1.2 节：“传输参数命令”。

调用 、、 或 方法后更改UsePassive会导致InvalidOperationException异常。BeginGetResponseGetResponseBeginGetRequestStreamGetRequestStream

如果 UsePassive 设置为 true，则 FTP 服务器可能不会发送文件大小，并且下载进度可能始终为零。 如果 UsePassive 设置为 false，防火墙可能会引发警报并阻止文件下载。

另请参阅

• FtpWebResponse
• FtpStatusCode
• WebRequestMethods.Ftp
• WebRequest
• WebResponse
• WebClient